Question

what happens to pressure in earth the deeper in earth

Answer 1

Pressure increases as you go deeper into Earth because every layer of rock has to support the weight of all the rock above it. In other words, pressure at depth z is the integral of density times gravity over the overlying column:

p(z) = p(surface) + ∫0^z ρ(z') g(z') dz'

Near the surface the pressure gradient is about ρg ≈ (3,000–3,300 kg/m3)(9.8 m/s2) ≈ 30–33 MPa per km (0.03–0.033 GPa/km). Some useful approximate values:

- Surface: ~0 GPa (atmospheric pressure is negligible for deep-Earth numbers)
- 10 km: ~0.3 GPa
- Moho (base of continental crust, ~35 km): ~1 GPa
- 100 km: ~3 GPa
- 410 km (mantle phase change): ~13–14 GPa
- 660 km (another mantle phase change): ~23–24 GPa
- Core–mantle boundary (~2,900 km): ~135–140 GPa
- Earth’s center (~6,371 km): ~360–370 GPa

These are approximate because rock density and gravity change with depth (density generally increases toward the center and gravity first stays similar then decreases toward zero at the center). The rising pressure causes minerals to change crystal structure, affects melting points, and is why the outer core is liquid while the inner core is solid.

If you want, I can show the integral calculation with a simple density model or plot pressure vs depth.